Characterization of chemical bonding features and defect state density in HfSiO x N y/SiO 2 gate stack

Abstract

We have studied depth profiling of the chemical composition, bonding features and defect states in 2 nm-thick HfSiO xN y (Hf/(Hf+Si) = ∼ 43%) films with N content of ∼13 at.% before and after post-deposition annealing (PDA) at 1050 °C in O 2 and N 2 ambience by using high-resolution x-ray photoelectron spectroscopy (XPS) and total photoelectron yield spectroscopy (PYS) in combination with oxide thinning by a dilute HF solution. NO x and Hf-N x ( x = 2, 3) bonding units existing in the sample before PDA were effectively eliminated or reduced by PDA and Si-N and Hf-N bonds were the main N bonding features after PDA. We found the formation of a region with a low Si content and a residue of Hf-N 2 bonding units in the HfSiO xN y film by O 2-PDA in comparison to N 2-PDA. The PYS measurements revealed a high density of filled defect states in such a Si-deficient region with a large number of Hf-N 2 bonds.